a. Field of the Invention
The present invention pertains generally to ablation catheters and electrode assemblies. More particularly, the present invention is directed toward ablation electrode assemblies for use in the human body having a mechanism for irrigating targeted areas. The present invention also relates to methods for improved assembly and accurate measurement and control of the electrode temperatures while effectively irrigating the targeted areas.
b. Background Art
Electrophysiology catheters are used for an ever-growing number of procedures. For example, catheters are used for diagnostic, therapeutic, and ablative procedures, to name just a few examples. Typically, the catheter is manipulated through the patient's vasculature and to the intended site, for example, a site within the patient's heart.
The catheter typically carries one or more electrodes, which may be used for ablation, diagnosis, or the like. There are a number of methods used for ablation of desired areas, including for example, radiofrequency (RF) ablation. RF ablation is accomplished by transmission of radiofrequency energy to a desired target area through an electrode assembly to ablate tissue at the target site.
Because RF ablation may generate significant heat, which if not carefully monitored and/or controlled can result in protein denaturation, blood coagulation, excess tissue damage, such as steam pop, tissue charring, and the like, it is desirable to monitor the temperature of the ablation assembly. It is further desirable to include a mechanism to irrigate certain target areas with biocompatible fluids, such as saline solution. This irrigation reduces or avoids excess, unwanted tissue damage, and blood coagulation and problems associated therewith. However, introduction of this irrigation solution may inhibit the ability to accurately monitor and/or control the temperature of the ablation assembly during use.
There are typically two classes of irrigated electrode catheters, open and closed irrigation catheters. Closed ablation catheters typically circulate a cooling fluid within the inner cavity of the electrode. Open ablation catheters, on the other hand, typically deliver the cooling fluid through open orifices on the electrode. Examples of these known catheters include the THERMOCOOL brand of catheters marketed and sold by Biosense-Webster. The current open irrigated ablation catheters use the inner cavity of the electrode, or distal member, as a manifold to distribute saline solution. The saline thus flows directly through the open orifices of the distal electrode member. This direct flow through the distal electrode tip lowers the temperature of the distal tip during operation, rendering accurate monitoring and control of the ablative process more difficult.
In these open electrode irrigated catheters, it has been determined that insulating the irrigation channels from the ablation electrode is beneficial. One such example was published on or around March 2005 in an article entitled “Saline-Irrigated Radiofrequency Ablation Electrode with Electrode Cooling,” by Drs. Wittkampf and Nakagawa et al., the content of which is hereby incorporated by reference in its entirety. Similarly, the content of PCT International Publication No. WO 05/048858, published on Jun. 2, 2005, is hereby incorporated by reference in its entirety.